BACKGROUND End-to-side neurorrhaphy is a promising procedure for nerve repair in peripheral nerve injury. However, in previous studies, this technique was limited to somatic nerves. The present study was designed to investigate the feasibility of nerve regeneration after end-to-side neurorrhaphy between autonomic nerve and somatic nerve. METHODS Thirty adult male Sprague-Dawley rats were randomly divided into the following three groups (n = 10 per group) for different treatments: (1) end-to-side neurorrhaphy group, the left L6 and S1 spinal nerves were transected in the dura, and the distal stump of L6 ventral root (L6VR) was sutured to the lateral face of L4 ventral root (L4VR) through end-to-side coaptation; (2) no repair group, the rats received the same operation as the end-to-side neurorrhaphy group but without coaptation; (3) control group, the rats received the same operation as the end-to-side neurorrhaphy group but the L6VR was preserved. After 4 month, the origin and mechanism of nerve regeneration were evaluated by retrograde nerve tracing. Morphologic and functional properties of the regenerated nerve were investigated by morphologic examination and intravesical pressure measurement. RESULTS Retrograde nerve tracing indicated that the new neural reflex pathway was successfully established, and the main regeneration mechanism was axon collateral sprouting. Morphologic examination and intravesical pressure measurement indicated prominent axonal regeneration and good bladder functional rehabilitation in the neurorrhaphy group. Wet weight and morphology of left extensor digitorum longus muscles appeared no detrimental effect on the donor nerve. CONCLUSIONS These results indicated that the somatic motor axons growth into autonomic nerve may be achieved through axon collateral sprouting for nerve repair and function rehabilitation after end-to-side neurorrhaphy of autonomic nerve and somatic nerve without apparent impairment of the donor somatic nerve.